1. Field of the Invention
This invention relates to an automotive air conditioning system, and more particularly, to a damper position control device for an automotive air conditioning system having an angular position control mechanism for a gear of a motor actuator, which regulates the angular position of an air mix damper.
2. Description of the Prior Art
FIG. 1 depicts a schematic view of a damper position control device used for an automotive air conditioning system. Air mix damper 1 is disposed between an evaporator and a heater core in a flow channel in which air flows in a path (not shown) from evaporator (not shown) past air mix damper 1 and to heater core (not shown). Air mix damper 1 controls the volume of air which flows to the heater core as a function of its angular position and, thereby, controls the temperature of the air in the flow channel. The damper position control device includes an electric power source 2, an electric power source switch device 3, and a motor actuator 4 which is operatively connected to air mix damper 1 through a wire or link and which varies the angular position of air mix damper 1.
Motor actuator 4 comprises a motor 41, a gear 42 connected to the drive shaft of motor 41, and a rotation control device 43 which controls the drive shaft of motor 41 and gear 42. Gear 42 is operatively connected to air mix damper 1 through a wire or link. Rotation control device 43 includes a regulator 44 which regulates the upper and lower rotational limits of gear 42.
Regulator 44 includes a movable contact 441 and fixed contacts 442a, 442b, and 442c. Movable contact 441 is rotationally driven in accordance with the rotation of the drive shaft of motor 41 and gear 42, and fixed contacts 442a, 442b, and 442c are in contact with movable contact 441. Fixed contacts 442a, 442b, and 442c are resistance elements disposed parallel to each other. Fixed contacts 442b and 442c are shorter than fixed contact 442a, and are disposed, so that they may be offset to the right and left, respectively. The upper and lower rotational limits of gear 42 are governed by the connections between fixed contacts 442b and 442c and movable contact 441. Fixed contacts 442b and 442c are coupled with motor 41 through diodes 45a and 45b, which have opposite polarities. Fixed contact 442a is coupled directly with electric power source switch device 3.
Switch device 3 includes switches 31 and 32 which are moveable, so that they may be linked together. Switch 31 comprises a movable contact 311 which is coupled with fixed contacts 442b and 442c through motor 41, and terminals 312a and 312b which may be brought into contact with movable contact 311 and, thereby, coupled with the positive and negative poles of electric power source 2, respectively. Switch 32 comprises a movable contact 321 which is coupled with fixed contact 442a, and terminals 322a and 322b which may be brought into contact with movable contact 321 and, thereby, coupled with the negative and positive poles of electric power source 2, respectively.
The damper position control device, discussed above, operates according to the following description. If movable contact 441 is initially positioned, such that it is in contact with the right end portions of fixed contacts 442a and 442b, as shown by the thatched, solid-line representation of contact 441, when movable contacts 311 and 321 are brought into contact with terminals 312a and 322a, respectively; electric current flows to motor 41 from electric power source 2 through fixed contacts 442a and 442b and movable contact 441. For example, terminals 312a and 322a may be brought into contact with contacts 311 and 321, respectively, by signals generated from a temperature control device and may be based on a predetermined temperature, an outside temperature, and a temperature inside an automobile passenger compartment. The drive shaft of motor 41 and gear 42 may rotate forward in response to the supply of electric current to motor 41. Air mix damper 1 is rotated forward in accordance with the rotation of gear 42. Moreover, movable contact 441 moves left along fixed contacts 442a and 442b, as shown by arrow A, in accordance with the rotation of gear 42. Thus, air mix damper 1 rotates and movable contact 441 moves during the rotation of gear 42.
Movable contact 441 is no longer in contact with the left end portion of fixed contact 442b when movable contact 441 reaches the left end portions of fixed contacts 442a and 442c. The final position of contact 441 is indicated by the broken-line representation of movable contact 441. Accordingly, the supply of electric current to motor 41 is cut off when the connection between movable contact 441 and fixed contact 442b is severed. When this connection is severed, the rotations of the drive shaft of motor 41 and gear 42 cease. Air mix damper 1 also stops at a fixed angular position in response to the cessation of the rotation of gear 42.
On the other hand, if movable contact 441 is initially positioned, so that it is in contact with the left end portions of fixed contacts 442a and 442c, as shown by the broken-line representation, when movable contacts 311 and 321 are brought into contact with terminals 312b and 322b, respectively, by signals generated by a temperature control device based on a predetermined temperature, an outside temperature, and an inside temperature; electric current flows to motor 41 from electric power source 2 through fixed contacts 442a and 442c and movable contact 441. When contact 441 is in this position, the drive shaft of motor 41 and gear 42 rotate in the opposite direction when electric current is supplied to motor 41. Air mix damper 1 also rotates in the opposite direction in accordance with the rotation of gear 42. Moreover, movable contact 441 moves right along fixed contacts 442a and 442c, as shown by arrow B, in accordance with the rotation of gear 42. Thus, air mix damper 1 rotates and movable contact 441 moves during the rotation of gear 42.
Movable contact 441 is no longer in contact with the right end portion of fixed contact 442c when movable contact 441 reaches the right end portions of fixed contacts 442a and 442b, as shown by the thatched, solid-line representation. Accordingly, the supply of electric current to motor 41 is cut off when the connection between movable contact 441 and fixed contact 442c is severed. When this connection is severed, the rotations of the drive shaft of motor 41 and gear 42 cease. Air mix damper 1 also stops at the fixed angular position in response to the cessation of the rotation of gear 42.
Thus, in the damper position control device, described above, the operating angles of air mix damper 1 are determined by the length and the position of fixed contacts 442b and 442c. Nevertheless, each of fixed contacts 442b and 442c can determine only one operating angle of air mix damper 1, and if it is necessary to increase the number of operating angles of air mix damper 1, the number of fixed contacts may have to be increased. Accordingly, regulator 44 and, therefore, damper position control device may become larger, heavier, and more complicated in order to increase the operating angles of air mix damper 1.